move image-related functions out of cmd/kpod/common.go and into libkpod/image

Signed-off-by: Ryan Cole <rcyoalne@gmail.com>

libkpod/image/image.go

@@ -1 +1,58 @@
 package image
+
+import (
+	is "github.com/containers/image/storage"
+	"github.com/containers/storage"
+	"github.com/kubernetes-incubator/cri-o/libkpod/image"
+	"github.com/pkg/errors"
+)
+
+// FindImage searches for an image with a matching the given name or ID in the given store
+func FindImage(store storage.Store, image string) (*storage.Image, error) {
+	var img *storage.Image
+	ref, err := is.Transport.ParseStoreReference(store, image)
+	if err == nil {
+		img, err = is.Transport.GetStoreImage(store, ref)
+	}
+	if err != nil {
+		img2, err2 := store.Image(image)
+		if err2 != nil {
+			if ref == nil {
+				return nil, errors.Wrapf(err, "error parsing reference to image %q", image)
+			}
+			return nil, errors.Wrapf(err, "unable to locate image %q", image)
+		}
+		img = img2
+	}
+	return img, nil
+}
+
+// Size returns the size of the image in the given store
+func Size(store storage.Store, img storage.Image) (int64, error) {
+	is.Transport.SetStore(store)
+	storeRef, err := is.Transport.ParseStoreReference(store, "@"+img.ID)
+	if err != nil {
+		return -1, err
+	}
+	imgRef, err := storeRef.NewImage(nil)
+	if err != nil {
+		return -1, err
+	}
+	imgSize, err := imgRef.Size()
+	if err != nil {
+		return -1, err
+	}
+	return imgSize, nil
+}
+
+// TopLayer returns the ID of the top layer of the image
+func getTopLayerID(img storage.Image) (string, error) {
+	metadata, err := image.ParseMetadata(img)
+	if err != nil {
+		return "", err
+	}
+	// Get the digest of the first blob
+	digest := string(metadata.Blobs[0].Digest)
+	// Return the first layer associated with the given digest
+	return metadata.Layers[digest][0], nil
+}